1. Field of the Invention
This invention relates generally to branch pipe lining techniques, and more particularly, to a branch pipe liner bag for lining an inner wall of a branch pipe which joins a main pipe. This invention is also relates to a branch pipe lining method which uses the branch pipe liner bag.
2. Description of the Related Art
When an underground pipe, such as pipelines and passageways, becomes defective or too old to perform properly, the pipe is repaired and rehabilitated without digging the earth to the pipe and disassembling the sections of the pipe. This non-digging method of repairing an underground pipe has been known and practiced commonly in the field of civil engineering. The pipe lining method utilizes a tubular pipe liner bag made of a resin-absorbent material impregnated with a hardenable resin, and having the outer surface covered with a highly air-tight plastic film. The tubular pipe liner bag is inserted into a pipe to be repaired by means of a pressurized fluid such that the pipe liner bag is turned inside out as it proceeds deeper in the pipe. Hereinafter, this manner of insertion shall be called "everting". When the entire length of the tubular liner bag is everted (i.e., turned inside out) into the pipe, the everted tubular liner is pressed against the inner wall of the pipe by a pressurized air, and the tubular flexible liner is hardened as the hardenable resin impregnated in the liner is heated, which is effected by heating the fluid filling the tubular liner bag. It is thus possible to line the inner wall of the defective or old pipe with a rigid liner without digging the ground and disassembling the pipe sections. The foregoing pipe lining method can be similarly applied to the lining of a main pipe of sewerage pipes or the like and a branch pipe branched off the main pipe.
A specific example of the conventional branch pipe lining method will be described with reference to FIGS. 16 and 17.
FIGS. 16 and 17 are cross-sectional views illustrating steps of a conventional branch pipe lining method. A branch pipe 131, a main pipe 130 in which a robot 122, a pressure bag 123 and other necessary tools and materials have been introduced. A branch pipe liner bag 101 has been inserted in the pressure bag 123.
The branch pipe liner bag 101 has a tubular resin-absorbent material having a flange 101A formed at one end, and impregnated with unhardened liquid hardenable resin. Near the flange 101A of the tubular resin-absorbent material, one end of a separable tube 140 is temporarily adhered such that the separable tube 140 can be torn off. The branch pipe liner bag 101 has the flange 101A carried on a collar 124 supported by the above-mentioned robot 122, and an uneverted portion of the resin-absorbent material except for the flange 101A has been inserted in the pressure bag 123.
An open end of the separable tube 140 attached to the branch pipe liner bag 101 is coupled to the pressure-bag 123 through a socket 128, and the collar 124 and the socket 128 are coupled by an elbow bag 129.
In operation, the robot 122 is driven to move the collar 124 upward to bring the flange 101A of the branch pipe liner bag 101 into close contact with the periphery of a branch pipe opening of the main pipe 130 (a portion of the main pipe 130 open to the branch pipe 131). Then pressurized air is supplied into a closed space S formed within the pressure bag 123 by the branch pipe liner bag 101 and the separable tube 140, causing the branch pipe liner bag 101 to be everted and inserted into the branch pipe 131 from the main pipe 130 toward the ground by the pressure of the air, as illustrated in FIG. 16. In this event, the separable tube 140 serves as a seal for air-tight sealing the branch pipe liner bag 101 and the pressure bag 123 to prevent the pressurized air within the closed space S from leaking.
Once the branch pipe liner bag 101 has been everted and inserted into the branch pipe 131 as described above, the hardenable resin impregnated in the branch pipe liner bag 101 is hardened with the branch pipe liner bag 101 remaining pressed onto the inner wall of the branch pipe 131, thus lining the branch pipe 131 with the hardened branch pipe liner bag 101. In this way, the branch pipe 131 is repaired.
Afterwards, the collar 124 is moved downward, and the flange 101A of the branch pipe liner bag 101 is removed from the collar 124, as illustrated in FIG. 17. Then, the pressure bag 123 and the robot 122 are pulled, for example, in a direction indicated by the arrow, causing the separable tube 140, which has been temporarily adhered to the tubular resin-absorbent material of the branch pipe liner bag 101, to be torn off the temporarily adhered portion of the tubular resin absorbent material. Then, the separable tube 140 is removed from the main pipe 130 together with the pressure bag 123 and the robot 122, thus completing a sequence of lining operations for the branch pipe 131.
Actually, however, branch pipes often have bent or curved portions. For passing a branch pipe liner bag through such a curved portion of a branch pipe, this requires a large everting pressure approximately five to ten times higher than that required for passing the branch pipe liner bag through a straight portion of a branch pipe. When the branch pipe liner bag is everted by applying a high everting pressure thereto for passing the branch pipe liner bag through a curved portion, a separable tube temporarily adhered thereto also receives large pressure and is possibly torn off the temporarily adhered portion.
To solve this problem, it is contemplated that a larger temporarily adhering force is provided for the separable tube. However, a larger temporarily adhering force, if provided for the separable tube, would result in a problem that the separable tube is not torn off the temporarily adhered portion, but instead the separable tube itself is broken in the middle.
As an alternative, when the separable tube is made stronger so as to prevent the same from breaking in the middle, a softened plastic-film, heated by a heat medium used for heating the thermosetting resin and heat generated by the hardening of the thermosetting resin, is peeled off the surface of the hardened tubular resin-absorbent material.